The Office of Fair Trading (OFT), the U.K. consumer watchdog, has requested a say in the proposed merger of the British divisions of mobile telecoms companies Orange and T-Mobile.

France Telecom owns Orange and Deutsche Telekom owns T-Mobile.

The OFT said it had asked the European Commission to let it scrutinize the deal because of concerns it could threaten competition in mobile telecommunications in the U.K.

In November 2009, T-Mobile and Orange agreed to form a joint venture in the U.K., which would make the new combined company the market leader with a 37% market share.

European regulators could have made a decision on the merger this month, but if the European Commission agrees to the U.K. request then it will likely take at least another six months. If its request is approved, the OFT would then decide whether the proposed merger needs to be investigated by the U.K.'s competition regulator, the Competition Commission.

"We are confident that any concerns about the venture can be dispelled and fundamentally believe that the deal is beneficial to competition," a Deutsche Telekom spokesman said.

The European Commission's EU executive has extended the deadline of its review to March 1 so it can consider the OFT request.